This invention concerns a color measuring method and device for printed matter, and in particular, concerns a color measuring method and device by which the differences in measurement results according to light source can be corrected. In many cases in the printing industry, the color of a specific part of each individual printed matter must be ascertained as an objective, numerical value. Various color measuring methods for printed matter have thus been known conventionally and various color measuring devices are actually being used.
In general, the color of an object is determined by the spectral reflectance of the object, the spectral intensity distribution of the light that illuminates the object, and the spectral sensitivity distribution of the visual system of the human being who is observing the object. A spectral reflectance that is measured for an object will thus be an important set of objective data that indicate the color of the object. However, the color of an object is also strongly affected by the spectral intensity distribution of the light that illuminates the object, in other words, by the spectral intensity distribution of the light source. Thus, for example, under a light source that contains a high amount of a red color component, the color of the object will be observed to be reddish. Therefore, the spectral intensity distribution of the light source is normally taken into consideration in measuring a spectral reflectance of an object.
To be more specific, the measurement of a spectral reflectance of a sample that is to be measured is carried out for example by the following method. First, a xe2x80x9cperfect reflecting diffuserxe2x80x9d, which is a plate-like object with a smooth surface that does not reflect light specularly and has a spectral reflectance of substantially close to 1.0 across the entire visible range, is prepared. Normally, a plate having barium sulfate or other white powder coated and solidified on the surface is used as the perfect reflecting diffuser. Next, a specific light source is made to illuminates the sample and the spectral intensity distribution of the reflected light that is obtained from the sample at this time is obtained. Next, light is irradiated onto the perfect reflecting diffuser using exactly the same light source and the spectral intensity distribution of the reflected light that is obtained from the perfect reflecting diffuser is obtained. As a device for measuring the spectral intensity distribution, a spectral radiance meter, etc., is generally used. Lastly, by dividing the spectral intensity distribution obtained for the sample by the spectral intensity distribution obtained for the perfect reflecting diffuser, the spectral reflectance of the sample that is not dependent on the light source can be obtained.
When the spectral reflectance of the sample has been obtained in the above manner, elements of the spectral sensitivity distribution of the human visual system are incorporated to provide data that objectively indicate the color that a human being senses in the observation process. The spectral reflectance data are data that indicate the reflectance in the visible wavelength range of 380 nm to 780 nm, and even if data are collected at each 5 nm of wavelength, the data will consist of numerical values indicating 81 values of reflectance and will thus be inconvenient to handle. Thus for color evaluation, a color is generally expressed using the tristimulus values (XYZ) of the XYZ colorimetric system stipulated by the Commission Internationale de l""Eclairage (CIE). The tristimulus values (XYZ) can be determined by a known method (refer for example to ISO/CIE 10527 CIE standard colorimetric observers, 1st Ed., 1991), which uses the spectral reflectance of the sample, the spectral sensitivity distribution of the human visual system, and the spectral intensity distribution of the light source that is used in observation, and are generally referred to as colorimetric values. As the spectral intensity distributions of typical light sources, the spectral intensity distributions, for example, of CIE standard illuminant D65, CIE illuminant D50, etc., which are stipulated in ISO/CIE 10526 CIE standard color illuminants, 1st Ed., 1991 can be used. Also with regard to the spectral sensitivity distribution of the human visual system, the color matching function for the XYZ colorimetric system stipulated in ISO/CIE 10527 CIE standard colorimetric observers, 1st Ed., 1991 can be used.
A general color measuring device for printed matter in the prior art has functions of measuring the color of a specific part of a printed matter based on the above-described principles of measuring color and determining objective data, such as the spectral reflectance, colorimetric values, etc. That is, a general color measuring device has a light source which illuminates light onto a printed matter that is to be measured, a spectral radiance meter which measures the spectral reflectance, and a computational processing unit which carries out various computations, and normally, a perfect reflecting diffuser is provided for carrying out corrections. When an operator performs the necessary computations in accordance to the above-described measurement procedure, the computational processing unit executes the necessary computations based on the collected data and thereby automatically obtains the spectral reflectance, colorimetric values, and other objective data.
With the above-described color measuring method, it should be possible to determine the spectral reflectance and colorimetric values of a sample that do not depend on the light source by carrying out the correction that makes uses of measurement results obtained using a perfect reflecting diffuser. However, in actuality, with a printed matter with which gradation is expressed by an area modulation method, such as offset printing, the measurement results obtained by a conventional color measuring method do not match the colors recognized by a human being in many cases. This is due to a fluorescent whitening (brightening) agent being contained in the printing paper. A fluorescent whitening agent is a colorless compound, which has the property of dyeing fibrous matter and emitting blue to purple fluorescent light corresponding to a wavelength near 420 nm and has the function of whitening the printed paper by emitting light that is complementary to the yellow color of fibers. To be more specific, stilbenzene dyes, etc. are used as fluorescent whitening agents in many printing papers. Though a sheet of paper that is comprised only of normal fibers looks yellowish, a sheet of paper to which a fluorescent whitening agent is added is increased in whiteness due to complementation by a blue to purple color (complementary color of yellow).
However, the intensity of fluorescence is normally strongly dependent on the wavelength of the light source, and a fluorescent whitening agent has the property of fluorescing strongly when illuminated with light of a high amount of ultraviolet components and weakening in fluorescence when illuminated with light of a low amount of ultraviolet components. Paper to which a fluorescent whitening agent is added thus seems bluish when observed under a fluorescent lamp, daytime sunlight, or other light source that contains a high amount of ultraviolet components and seems yellowish when observed under an illumination light source, such as a tungsten lamp. In a printed matter with which gradation is expressed by an area modulation method, such as offset printing, ink is transferred to a paper as a collection of microscopic units of adhesion (halftone dots in the case of offset printing). Gradation is expressed by this units of ink by controlling the area of the ink-adhered part per unit area, in other words the dot percent. The same applies likewise to color printed matter obtained by an inkjet printer. Thus with a halftone printed matter, the bare part of the paper to which ink is not adhered becomes an important element that affects color. For example, a halftone part for which the offset printing dot percent is 50% magenta is observed as a pink-colored part. However, in actuality, a magenta part (ink-adhered part) and a bare part (white paper part) are simply observed in a mixed manner at a fifty-fifty ratio. Thus when the paper contains a fluorescent whitening agent, the actually observed color is greatly affected by the type of light source.
Generally in a color measuring device, a tungsten lamp is used in many cases to make the size of the device itself compact. Thus under the measuring environment of such a color measuring device, the emission of fluorescence from the fluorescent whitening agent contained in the paper will be extremely weak. In other words, the spectral reflectance and colorimetric values obtained by a color measuring device that uses a tungsten lamp as a light source are measurement results obtained under conditions where the fluorescence from the fluorescent whitening agent contained in the paper is weak. However, when the same printed matter is observed under a fluorescent lamp or daytime sunlight, since the fluorescent whitening agent fluoresces strongly, the color will be observed to differ from the color indicated by the measurement results that were obtained under conditions of weak fluorescence. Due to such causes, there is the problem that the measurement results obtained by the prior-art color measuring method does not necessarily match the color recognized by a human occurs in the case of a printed matter that uses paper containing a fluorescent whitening agent.
This invention has been made to resolve the above-described problem and an object thereof is to provide a color measuring method and device for printed matter by which correct color evaluation standards can be indicated even when a printed matter is observed under a light source that differs from the light source used in the color measuring process.
(1) The first feature of the present invention resides in a color measuring method for determining a spectral reflectance, under a predetermined illumination environment, for a printed matter including a paper containing a fluorescent whitening agent, the method being comprised of:
a first step of measuring a spectral reflectance Pt(xcex) of the paper under a first illumination environment and a spectral reflectance Pu(xcex) of the paper under a second illumination environment;
a second step of computing a difference, obtained by subtracting the spectral reflectance Pt(xcex) from the spectral reflectance Pu(xcex), as a differential component Fp(xcex) of the paper due to the fluorescent whitening agent;
a third step of measuring a spectral reflectance Rt(xcex), under the first illumination environment, for a region to be measured of the printed matter; and
a fourth step of performing a correction based on the differential component Fp(xcex) on the spectral reflectance Rt(xcex) to compute an estimated spectral reflectance, under the second illumination environment, for the region to be measured.
(2) The second feature of the present invention resides in a color measuring method for printed matter including the first feature, wherein:
in a process of measurement in the first step and the third step, a result of measurement of a spectral reflectance of a perfect reflecting diffuser is used to perform a correction of eliminating influence of spectral intensity distribution of illumination light that is used.
(3) The third feature of the present invention resides in a color measuring method for printed matter including the first or second feature, wherein:
in a process of computation in the fourth step, correction based on the differential component Fp(xcex) is not performed on an ink-adhered region within the region to be measured.
(4) The fourth feature of the present invention resides in a color measuring method for printed matter including the third feature, wherein:
in the third step, a spectral reflectance Rt(xcex, S) under the first illumination environment is measured for a region to be measured, a ratio of an area of an ink-adhered region to an entire area in the region to be measured being S;
in the fourth step, a computation using an equation:
Rtu(xcex, S)=Rt(xcex, S)+Fp(xcex)xc2x7(1xe2x88x92S)2 
xe2x80x83is performed to determine an estimated spectral reflectance Rtu(xcex, S), under the second illumination environment, for the region to be measured.
(5) The fifth feature of the present invention resides in a color measuring method for printed matter including the first or second feature, wherein:
in a process of computation in the fourth step, a correction based on the differential component Fp(xcex) is performed in accordance to an optical transmittance of an ink layer for an ink-adhered region in the region to be measured.
(6) The sixth feature of the present invention resides in a color measuring method for printed matter including the fifth feature, wherein:
in the third step, a spectral reflectance Rt(xcex, S) under the first illumination environment is measured for a region to be measured, a ratio of an area of an ink-adhered region to an entire area in the region to be measured being S;
in the fourth step, an excitation coefficient CE and a luminescence coefficient CL are defined, the excitation coefficient CE indicating a proportion of xe2x80x9ctotal amount of excitation energy supplied to an ink-adhered partxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of excitation energy supplied to a non-ink-adhered partxe2x80x9d per unit area in the case where the parts are illuminated under the same conditions from an exterior, the luminescence coefficient CL indicating a proportion of xe2x80x9ctotal amount of luminescence energy emitted from the ink-adhered part and observedxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of luminescence energy emitted from the non-ink-adhered part and observedxe2x80x9d per unit area in the case where emission of fluorescence from each of the parts occurs under the same conditions inside the paper, the excitation coefficient CE and the luminescence coefficient CL of the region to be measured are measured, and computation using an equation:
RRtu(xcex, S)=Rt(xcex, S)+Fp(xcex)xc2x7(1xe2x88x92S(1xe2x88x92CE))xc2x7(1xe2x88x92S(1xe2x88x92CL)) 
xe2x80x83is performed to determine an estimated spectral reflectance RRtu(xcex, S), under the second illumination environment, for the region to be measured.
(7) The seventh feature of the present invention resides in a color measuring method for printed matter including the fifth feature, wherein:
in the third step, a spectral reflectance Rt(xcex, S1, S2, S12) under the first illumination environment is measured for a region to be measured, ratios of areas of a first region, a second region, a third region and a fourth region with respect to an entire area in the region to be measured being S1, S2, S12, Sp, respectively, only a first ink being adhered in the first region, only a second ink being adhered in the second region, both the first ink and the second ink being adhered in the third region, and neither ink being adhered in the fourth region;
in the fourth step, an excitation coefficient CE and a luminescence coefficient CL are defined, the excitation coefficient CE indicating a proportion of xe2x80x9ctotal amount of excitation energy supplied to an ink-adhered partxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of excitation energy supplied to a non-ink-adhered partxe2x80x9d per unit area in the case where the parts are illuminated under the same conditions from an exterior, the luminescence coefficient CL indicating a proportion of xe2x80x9ctotal amount of luminescence energy emitted from the ink-adhered part and observedxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of luminescence energy emitted from the non-ink-adhered part and observedxe2x80x9d per unit area in the case where emission of fluorescence from each of the parts occurs under the same conditions inside the paper, excitation coefficients CE1, CE2, and CE12 and luminescence coefficients CL1, CL2, and CL12 of the first region, the second region, and the third region, respectively, are measured, and computation using an equation:
RRtu(xcex, S1, S2, S12)=Rt(xcex, S1, S2, S12)+Fp(xcex)xc2x7(Sp+S1xc2x7CE1+S2xc2x7CE2+S12xc2x7CE12)xc2x7(Sp+S1xc2x7CL1+S2xc2x7CL2+S12xc2x7CL12) 
xe2x80x83is performed to determine an estimated spectral reflectance RRtu(xcex, S1, S2, S12), under the second illumination environment, for the region to be measured.
(8) The eighth feature of the present invention resides in a color measuring method for printed matter including the fifth feature, wherein:
in the third step, a spectral reflectance under the first illumination environment is measured for a region to be measured, on which printing using a plurality of inks is performed and a total of n kinds of ink-adhered regions are formed by mixing of a first type of region in which only an ink of a single color is adhered and a second type of region in which a plurality of inks are adhered in an overlapping manner, a ratio of an area of an i-th region with respect to an entire area in the region to be measured being Si;
in the fourth step, an excitation coefficient CE and a luminescence coefficient CL are defined, the excitation coefficient CE indicating a proportion of xe2x80x9ctotal amount of excitation energy supplied to an ink-adhered partxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of excitation energy supplied to a non-ink-adhered partxe2x80x9d per unit area in the case where the parts are illuminated under the same conditions from an exterior, the luminescence coefficient CL indicating a proportion of xe2x80x9ctotal amount of luminescence energy emitted from the ink-adhered part and observedxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of luminescence energy emitted from the non-ink-adhered part and observedxe2x80x9d per unit area in the case where emission of fluorescence from each of the parts occurs under the same conditions inside the paper, and the excitation coefficient CE and the luminescence coefficient CL of each of the n kinds of ink-adhered regions are measured; and
in a process of computation in the fourth step, a correction based on the differential component Fp(xcex) is performed on the n kinds of ink-adhered regions in the region to be measured in accordance to the excitation coefficients CE and the luminescence coefficients CL determined for the respective n kinds of ink-adhered regions.
(9) The ninth feature of the present invention resides in a color measuring method for printed matter including the sixth, seventh or eighth feature, wherein:
a spectral transmittance R(xcex) of the ink-adhered part, a spectral transmittance P(xcex) of the non-ink-adhered part, an excitation spectrum PE(xcex) of the paper, and a luminescence spectrum PL(xcex) of the paper are measured; and
the excitation coefficient CE and the luminescence coefficient CL of the ink-adhered part are determined using the following equations:
CE=∫R(xcex)xc2x7PE(xcex)dxcex/∫P(xcex)xc2x7PE(xcex)dxcex
CL=∫R(xcex)xc2x7PL(xcex)dxcex/∫P(xcex)xc2x7PL(xcex)dxcex. 
(10) The tenth feature of the present invention resides in a color measuring method for determining XYZ tristimulus values, under a predetermined illumination environment, for a printed matter including a paper containing a fluorescent whitening agent, the method being comprised of:
a first step of measuring XYZ tristimulus values Pt(X), Pt(Y), and Pt(Z) of the paper under a first illumination environment and XYZ tristimulus values Pu(X), Pu(Y), and Pu(Z) of the paper under a second illumination environment;
a second step of computing differences, obtained by subtracting the XYZ tristimulus values Pt(X), Pt(Y), and Pt(Z) from the XYZ tristimulus values Pu(X), Pu(Y), and Pu(Z), respectively, as differential components Fp(X), Fp(Y), and Fp(Z) of the paper due to the fluorescent whitening agent;
a third step of measuring XYZ tristimulus values Rt(X), Rt(Y), and Rt(Z), under the first illumination environment, for a region to be measured of the printed matter; and
a fourth step of performing corrections based on the differential components Fp(X), Fp(Y), and Fp(Z) on the XYZ tristimulus values Rt(X), Rt(Y), and Rt(Z), respectively, to compute estimated XYZ tristimulus values, under the second illumination environment, for the region to be measured.
(11) The eleventh feature of the present invention resides in a color measuring method for printed matter including the tenth feature, wherein:
in a process of measurement in the first step and the third step, XYZ tristimulus values are determined by computation using spectral reflectances obtained by measurement.
(12) The twelfth feature of the present invention resides in a color measuring method for printed matter including the tenth or eleventh feature, wherein:
in a process of computation in the fourth step, corrections based on the differential components Fp (X), Fp (Y), and Fp(Z) are not performed on an ink-adhered region within the region to be measured.
(13) The thirteenth feature of the present invention resides in a color measuring method for printed matter including the twelfth feature, wherein:
in the third step, XYZ tristimulus values Rt(X, S), Rt(Y, S), and Rt(Z, S) under the first illumination environment is measured for a region to be measured, a ratio of an area of an ink-adhered region to an entire area in the region to be measured being S;
in the fourth step, computations using the following equations:
Rtu(X, S)=Rt(X, S)+Fp(X)xc2x7(1xe2x88x92S)2 
Rtu(Y, S)=Rt(Y, S)+Fp(Y)xc2x7(1xe2x88x92S)2 
Rtu(Z, S)=Rt(Z, S)+Fp(Z)xc2x7(1xe2x88x92S)2 
xe2x80x83are performed to determine estimated XYZ tristimulus values Rtu(X, S), Rtu(Y, S), and Rtu(Z, S), under the second illumination environment, for the region to be measured.
(14) The fouteenth feature of the present invention resides in a color measuring method for printed matter including the tenth or eleventh feature, wherein:
in a process of computation in the fourth step, corrections based on the differential components Fp(X), Fp(Y), and Fp(Z) are performed in accordance to an optical transmittance of an ink layer for an ink-adhered region in the region to be measured.
(15) The fifteenth feature of the present invention resides in a color measuring method for printed matter including the fourteenth feature, wherein:
in the third step, XYZ tristimulus values Rt(X, S), Rt(Y, S), and Rt(Z, S) under the first illumination environment is measured for a region to be measured, a ratio of an area of an ink-adhered region to an entire area in the region to be measured being S;
in the fourth step, an excitation coefficient CE and a luminescence coefficient CL are defined, the excitation coefficient CE indicating a proportion of xe2x80x9ctotal amount of excitation energy supplied to an ink-adhered partxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of excitation energy supplied to a non-ink-adhered partxe2x80x9d per unit area in the case where the parts are illuminated under the same conditions from an exterior, the luminescence coefficient CL indicating a proportion of xe2x80x9ctotal amount of luminescence energy emitted from the ink-adhered part and observedxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of luminescence energy emitted from the non-ink-adhered part and observedxe2x80x9d per unit area in the case where emission of fluorescence from each of the parts occurs under the same conditions inside the paper, the excitation coefficient CE and the luminescence coefficient CL of the region to be measured are measured, and computations using the following equations:
RRtu(X, S)=Rt(X, S)+Fp(X)xc2x7(1xe2x88x92S(1xe2x88x92CE))xc2x7(1xe2x88x92S(1xe2x88x92CL)) 
RRtu(Y, S)=Rt(Y, S)+Fp(Y)xc2x7(1xe2x88x92S(1xe2x88x92CE))xc2x7(1xe2x88x92S(1xe2x88x92CL)) 
RRtu(Z, S)=Rt(Z, S)+Fp(Z)xc2x7(1xe2x88x92S(1xe2x88x92CE))xc2x7(1xe2x88x92S(1xe2x88x92CL)) 
xe2x80x83are performed to determine estimated XYZ tristimulus values RRtu(X, S), RRtu(Y, S), and RRtu(Z, S), under the second illumination environment, for the region to be measured.
(16) The sixteenth feature of the present invention resides in a color measuring method for printed matter including the fourteenth feature, wherein:
in the third step, XYZ tristimulus values under the first illumination environment are measured for a region to be measured, on which printing using a plurality of inks is performed and a total of n kinds of ink-adhered regions are formed by mixing of a first region in which only an ink of a single color is adhered and a second region in which a plurality of inks are adhered in an overlapping manner, a ratio of an area of an i-th region with respect to an entire area in the region to be measured being Si;
in the fourth step, an excitation coefficient CE and a luminescence coefficient CL are defined, the excitation coefficient CE indicating a proportion of xe2x80x9ctotal amount of excitation energy supplied to an ink-adhered partxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of excitation energy supplied to a non-ink-adhered partxe2x80x9d per unit area in the case where the parts are illuminated under the same conditions from an exterior, the luminescence coefficient CL indicating a proportion of xe2x80x9ctotal amount of luminescence energy emitted from the ink-adhered part and observedxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of luminescence energy emitted from the non-ink-adhered part and observedxe2x80x9d per unit area in the case where emission of fluorescence from each of the parts occurs under the same conditions inside the paper, and the excitation coefficient CE and the luminescence coefficient CL of each of the n kinds of ink-adhered regions are measured; and
in a process of computation in the fourth step, corrections based on the differential components Fp(X), Fp(Y), and Fp(Z) are performed on the n kinds of ink-adhered regions in the region to be measured in accordance to the excitation coefficients CE and the luminescence coefficients CL determined for the respective n kinds of ink-adhered regions.
(17) The seventeenth feature of the present invention resides in a color measuring method for printed matter including the fifteenth or sixteenth feature, wherein:
a spectral transmittance R(xcex) of the ink-adhered part, a spectral transmittance P(xcex) of the non-ink-adhered part, an excitation spectrum PE(xcex) of the paper, and a luminescence spectrum PL(xcex) of the paper are measured; and
the excitation coefficient CE and the luminescence coefficient CL of the ink-adhered part are determined using the following equations:
CE=∫R(xcex)xc2x7PE(xcex)dxcex/∫P(xcex)xc2x7PE(xcex)dxcex
CL=∫R(xcex)xc2x7PL(xcex)dxcex/∫P(xcex)xc2x7PL(xcex)dxcex. 
(18) The eighteenth feature of the present invention resides in a color measuring device for determining a spectral reflectance, under a predetermined illumination environment, of a printed matter including a paper containing a fluorescent whitening agent, the color measuring device being comprised of:
a spectral reflectance measuring device, which measures a spectral reflectance of an object to be measured under a first illumination environment;
a storage unit, which stores a differential component Fp(xcex), obtained by subtracting a spectral reflectance Pt(xcex) of a specific paper under the first illumination environment from a spectral reflectance Pu(xcex) of the paper under a second illumination environment; and
a computational processing unit, which performs a correction based on the differential component Fp(xcex) on a spectral reflectance Rt(xcex), which is measured by the spectral reflectance measuring device for a region to be measured in the printed matter including the specific paper, to compute an estimated spectral reflectance, under the second illumination environment, for the region to be measured.
(19) The nineteenth feature of the present invention resides in a color measuring devise for printed matter including the eighteenth feature, wherein:
the computational processing unit has a function of inputting an area ratio S of an ink-adhered region with respect to an entire area within the region to be measured and performs computation using the following equation on a spectral reflectance Rt(xcex, S), which has been measured for the region to be measured by the spectral reflectance measuring device;
Rtu(xcex, S)=Rt(xcex, S)+Fp(xcex)xc2x7(1xe2x88x92S)2 
xe2x80x83so as to determine an estimated spectral reflectance Rtu(xcex, S), under the second illumination environment, of the region to be measured.
(20) The twentieth feature of the present invention resides in a color measuring devise for printed matter including the nineteenth feature, wherein:
a dot percent measuring device, which measures an area ratio S of an ink-adhered region with respect to an entire area within the region to be measured, is furthermore equipped.
(21) The twenty-first feature of the present invention resides in a color measuring devise for printed matter including the eighteenth feature, wherein:
the computational processing unit has a function of inputting, with regard to the region to be measured, an area ratio S of an ink-adhered region with respect to an entire area, an excitation coefficient CE, which indicates a proportion of xe2x80x9ctotal amount of excitation energy supplied to the ink-adhered partxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of excitation energy supplied to a non-ink-adhered partxe2x80x9d per unit area in the case where the parts are illuminated under the same conditions from an exterior, and a luminescence coefficient CL, which indicates a proportion of xe2x80x9ctotal amount of luminescence energy emitted from the ink-adhered part and observedxe2x80x9d per unit area with respect to xe2x80x9ctotal amount of luminescence energy emitted from the non-ink-adhered part and observedxe2x80x9d per unit area in the case where emission of fluorescence from each of the parts occurs under the same conditions inside the paper, and performs computation using the following equation on a spectral reflectance Rt(xcex, S), which has been measured for the region to be measured by the spectral reflectance measuring device;
RRtu(xcex, S)=Rt(xcex, S)+Fp(xcex)xc2x7(1xe2x88x92S(1xe2x88x92CE))xc2x7(1xe2x88x92S(1xe2x88x92CL)) 
xe2x80x83so as to determine an estimated spectral reflectance RRtu(xcex, S), under the second illumination environment, of the region to be measured.
(22) The twenty-second feature of the present invention resides in a color measuring devise for printed matter including the twenty-first feature, furthermore equipped with:
a dot percent measuring device, which measures an area ratio S of an ink-adhered region with respect to an entire area within the region to be measured;
a transmittance measuring device, which measures a spectral transmittance R(xcex) of an ink-adhered part in the region to be measured and a spectral transmittance P(xcex) of a non-ink-adhered part in the region to be measured; and
a coefficient computation unit, which computes an excitation coefficient CE and a luminescence coefficient CL of the ink-adhered part, using the spectral transmittance R(xcex) and the spectral transmittance P(xcex) which have been measured by the transmittance measuring device, and an excitation spectrum PE(xcex) of the paper and a luminescence spectrum PL(xcex) of the paper in accordance to the following equations:
CE=∫R(xcex)xc2x7PE(xcex)dxcex/∫P(xcex)xc2x7PE(xcex)dxcex
CL=∫R(xcex)xc2x7PL(xcex)dxcex/∫P(xcex)xc2x7PL(xcex)dxcex. 
(23) The twenty-third feature of the present invention resides in a color measuring devise for printed matter including the twenty-second feature, wherein:
a spectrofluorometer, which measures an excitation spectrum PE(xcex) of the paper and a luminescence spectrum PL(xcex) of the paper, is furthermore equipped and the coefficient computation unit uses the excitation spectrum PE(xcex) of the paper and the luminescence spectrum PL(xcex) of the paper measured by the spectrofluorometer in performing computation for determining the excitation coefficient CE and the luminescence coefficient CL.
(24) The twenty-fourth feature of the present invention resides in a color measuring devise for printed matter including the eighteenth to twenty-third features, wherein:
the computational processing unit has a function of computing XYZ tristimulus values based on a predetermined spectral reflectance and computes estimated XYZ tristimulus values, under the second illumination environment, for the region to be measured.
(25) The twenty-fifth feature of the present invention resides in a color measuring devise for printed matter including the twenty-fourth feature, wherein:
the storage unit stores the differential component Fp(xcex) in a form of XYZ tristimulus values; and
the computational processing unit performs computation using the differential component stored in the form of XYZ tristimulus values.
(26) The twenty-sixth feature of the present invention resides in a program, which makes a computer function as the computational processing unit in a color measuring device for printed matter having the eighteenth to twenty-fifty features, or a computer-readable medium that stores the program.